text: 
  const drawerWidth = 240;
  const headerStyle = theme => ({
    appBar: {
      position: 'absolute',
      transition: theme.transitions.create(['margin', 'width'], {
        easing: theme.transitions.easing.sharp,
        duration: theme.transitions.duration.leavingScreen,
      }),
    },
    appBarShift: {
      width: `calc(100% - ${drawerWidth}px)`,
      transition: theme.transitions.create(['margin', 'width'], {
        easing: theme.transitions.easing.easeOut,
        duration: theme.transitions.duration.enteringScreen,
      }),
    },
    'appBarShift-left': {
      marginLeft: drawerWidth,
    },
    'appBarShift-right': {
      marginRight: drawerWidth,
    },
    menuButton: {
      marginLeft: 12,
      marginRight: 20,
    },
    hide: {
      display: 'none',
    }
  });
  
  export default headerStyle;